[vtkusers] Smooth shading

[Yoshinori KONISHI]

Hello all, 

Though I am trying to get a smooth shaded CAD object (.stl), 
the rendered image looks like that of flat shading (not smooth). 
Could anyone tell me how to correct my code ? 

--------------------------- (VTK 6.1.0 on Win7 64bit)
  vtkSmartPointer<vtkSTLReader> reader = vtkSmartPointer<vtkSTLReader>::New();
  reader->SetFileName(inputFilename.c_str());
  reader->Update();
  
  vtkSmartPointer<vtkPolyDataMapper>	cadMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
  cadMapper->SetInputConnection(reader->GetOutputPort());
  
  vtkSmartPointer<vtkActor>	cadActor = vtkSmartPointer<vtkActor>::New();
  cadActor->SetMapper(cadMapper);
  cadActor->GetProperty()->SetInterpolation(VTK_GOURAUD);
  
  vtkSmartPointer<vtkRenderer>	ren1 = vtkSmartPointer<vtkRenderer>::New();
  ren1->AddActor(cadActor);
  ren1->SetBackground(0.1, 0.2, 0.4);
  
  vtkSmartPointer<vtkRenderWindow>	renWin = vtkSmartPointer<vtkRenderWindow>::New();
  renWin->AddRenderer(ren1);
  renWin->SetSize(640, 480);
--------------------------------------

Thank you.